Impenetrability?

[steevey]

If an electron can appear pretty much anywhere, why can't it appear in the nucleus of an atom? You could argue impenetrability, but couldn't an electron just combine with a proton or just force other particles out of the way? An electron is pretty small compared to the other particles too, I'm sure there would be some gaps where the particles that make up an electron could fit. Even though an electron is a wave, why can't the wave ever touch the nucleus? No particle in the nucleus has the same exact quantum numbers as an electron, so there shouldn't even really be a problem with them canceling each other out.

Edited December 14, 2010 by steevey

[Mr Skeptic]

Go look at the shape of orbitals, and also (reverse) beta decay.

[steevey]

Go look at the shape of orbitals, and also (reverse) beta decay.

 

A wave function extends indefinitely through space though. Those "orbitals" are just the *most likely* places for those particles to show up. An electron could actually appear in any place in the universe, but the chances of it doing so are unimaginably small after you get past even 10*10^-9 meters, which is why the classical world is so different from the quantum world.

And what I'm talking about isn't a particle in the nucleus giving off an electron, I'm talking about an electron in "orbit" around an atom going from its orbital to actually being in the nucleus.

Edited December 14, 2010 by steevey

[Mr Skeptic]

Or you could be lazy and not bother to look it up. Electrons can be found in the nucleus too.

 

If what you mean is staying in the nucleus, then the energy, momentum, and wavelength considerations become significant. For example, if you want it to stay in the nucleus you'd want the wavelength not to be too much bigger than the nucleus. That will tell you how fast the electron would have to move, and then you need to compare to the force that would be holding it into the nucleus. There's also plenty of scam companies suggesting that they found a way to get tons of energy from (usually water) by having its electrons drop to an energy level lower than the first.

[steevey]

Or you could be lazy and not bother to look it up. Electrons can be found in the nucleus too.

 

If what you mean is staying in the nucleus, then the energy, momentum, and wavelength considerations become significant. For example, if you want it to stay in the nucleus you'd want the wavelength not to be too much bigger than the nucleus. That will tell you how fast the electron would have to move, and then you need to compare to the force that would be holding it into the nucleus. There's also plenty of scam companies suggesting that they found a way to get tons of energy from (usually water) by having its electrons drop to an energy level lower than the first.

 

If I'm asking this question here, then obviously google doesn't help.

 

 

The reason for an electron not falling into the nucleus is one of the main reasons why quantum mechanics exists, because in the previous standard model, en electron should fall into the nucleus. In our current theory that an electron really isn't even found in the nucleus. In quantum mechanics, an electron can sit in a position above the nucleus at the most minimum state of energy possible for an electron, the ground state without falling in. Quantum mechanics specifically prohibits an electron from even the ground state from just falling into the nucleus. But still, ****************WHY*************** isn't it ever found in the nucleus? Why don't I ever see anything anywhere about an electron going from an orbital to the nucleus?

Edited December 14, 2010 by steevey

[swansont]

As Mr Skeptic has tried to explain, your claim is false. Since the nucleus has a finite size, orbital electrons are found in the nucleus, particularly if they are in S-orbitals. They don't spend a lot of time there, but the probability of finding them there is nonzero. This explains the previously-mentioned reverse beta decay, as well as the relatively large hyperfine splitting of ground (s) states of alkali atoms vs the excited (p) state; the electron spends more time in and near the nucleus, so the magnetic interaction is stronger.

[steevey]

As Mr Skeptic has tried to explain, your claim is false. Since the nucleus has a finite size, orbital electrons are found in the nucleus, particularly if they are in S-orbitals. They don't spend a lot of time there, but the probability of finding them there is nonzero. This explains the previously-mentioned reverse beta decay, as well as the relatively large hyperfine splitting of ground (s) states of alkali atoms vs the excited (p) state; the electron spends more time in and near the nucleus, so the magnetic interaction is stronger.

 

Then why do so many other sources say electrons can't be in the nucleus? And how could the new standard model be based around electrons not being able to exist in the nucleus if they can in fact be in the nucleus? Physicists like Heisenberg and Max tried to come uo with a way to avoid electrons being able to fall into the nucleus, which is why they gave electrons a wave function. Also when I looked up "reverse" beta decay, I found this which says the electron is a result and not a cause, http://everything2.c...erse+beta+decay

 

I honestly could have sworn electrons could occasionally fall into the nucleus from their orbitals, but for some reason some quantum mechanical laws prohibit it.

Edited December 15, 2010 by steevey

[swansont]

There's unfortunately some ambiguity in the name. Try "electron capture" http://en.wikipedia.org/wiki/Electron_capture

 

The description of electrons falling into the nucleus from an orbital has a very Bohr-atom flavor to it. In the beginning of quantum mechanics, it was not understood what kept the electron from spiraling into the nucleus and neutralizing the the protons. But the presupposed classical orbits and trajectories and was being discussed before much of the behavior of nuclear and particle physics was known. Electrons cannot be confined to the nucleus, as mentioned earlier, so we know that a neutron is not simply a proton and electron bound together.